GeometricSampler (VirtualDataSet API)

java.lang.Object
- org.apache.commons.rng.sampling.distribution.GeometricSampler

All Implemented Interfaces:

DiscreteSampler
```
public class GeometricSampler
extends java.lang.Object
implements DiscreteSampler
```
Sampling from a geometric distribution.
This distribution samples the number of failures before the first success taking values in the set [0, 1, 2, ...].

The sample is computed using a related exponential distribution. If \( X \) is an exponentially distributed random variable with parameter \( \lambda \), then \( Y = \left \lfloor X \right \rfloor \) is a geometrically distributed random variable with parameter \( p = 1 − e^\lambda \), with \( p \) the probability of success.

This sampler outperforms using the InverseTransformDiscreteSampler with an appropriate Geometric inverse cumulative probability function.

Usage note: As the probability of success (\( p \)) tends towards zero the mean of the distribution (\( \frac{1-p}{p} \)) tends towards infinity and due to the use of int for the sample this can result in truncation of the distribution.

Sampling uses UniformRandomProvider.nextDouble().

Since:

1.3

See Also:

Geometric distribution - related distributions

- Constructor Summary
  
  Constructors
  Constructor Description
  
  GeometricSampler(UniformRandomProvider rng, double probabilityOfSuccess)
  Creates a new geometric distribution sampler.
- Method Summary
  
  Modifier and Type Method Description
  
  int sample()
  Create a sample from a geometric distribution.
  
  java.lang.String toString()
  - Methods inherited from class java.lang.Object
    clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - GeometricSampler
```
public GeometricSampler(UniformRandomProvider rng,
                        double probabilityOfSuccess)
```
    Creates a new geometric distribution sampler. The samples will be provided in the set k=[0, 1, 2, ...] where k indicates the number of failures before the first success.
    
    Parameters:
    
    rng - Generator of uniformly distributed random numbers
    
    probabilityOfSuccess - The probability of success
    
    Throws:
    
    java.lang.IllegalArgumentException - if probabilityOfSuccess is not in the range [0 < probabilityOfSuccess <= 1])
- Method Detail
  - sample
```
public int sample()
```
    Create a sample from a geometric distribution.
    The sample will take the values in the set [0, 1, 2, ...], equivalent to the number of failures before the first success.
    
    Specified by:
    
    sample in interface DiscreteSampler
    
    Returns:
    
    a sample.
  - toString
```
public java.lang.String toString()
```
    Overrides:
    
    toString in class java.lang.Object